Field of the Invention
The present invention relates to a water-based ink for ink-jet recording and an ink cartridge.
Description of the Related Art
Ink-jet recording is conventionally performed by using water-based pigment inks for ink-jet recording in which pigments are used as colorant. Such a water-based pigment ink typically suffers from the problem of rubbing resistance in which a part of the pigment jetted on a recording medium remains on a surface of the recording medium and the remaining pigment peels off from the recording medium when being rubbed by a finger or the like. In order to solve the problem, Japanese Patent Application laid-open No. 2006-273892 corresponding to United States Patent Application Publication Nos. 2009/0220748 and 2013/0235117 discloses an approach in which a polymer is added to the water-based pigment ink to improve the rubbing resistance on the recording medium.
However, adding the polymer to the water-based pigment ink in an excessive amount for the purpose of improving the rubbing resistance may cause the following problem. Namely, when moisture or water in the water-based pigment ink evaporates, the polymer increases the viscosity of the water-based pigment ink to affect maintenance performance. Further, recent ink-jet recording using the water-based ink for ink-jet recording needs higher quality images and higher speed operation. Thus, there is a need for a water-based pigment ink for ink-jet recording which has a good rubbing resistance in recording on glossy paper and which is less likely to cause the unevenness in recording on regular paper.
In view of the above, an object of the present teaching is to provide a water-based pigment ink for ink-jet recording which has a good rubbing resistance in recording on glossy paper and is less likely to cause the unevenness in recording on regular paper.